1. Field of the Invention
The present invention generally relates to reflector antennas, and more particularly relates to a method and apparatus that reduce the effects of collector surface blockage in reflector antennas while increasing antenna gain and efficiency.
2. Description of the Prior Art
Parabolic antennas have been used for many years as an inexpensive fixed beam antenna in both transmit and receive applications. FIG. 1 shows an example of a center-feed parabolic antenna 10, which has been in common use in backyards as a satellite reception antenna.
Center-feed parabolic antennas 10 work very well in such applications. However, when sidelobe reduction is either desired or required, performance of this type of reflector antenna is limited by blockage of its collector surface 12 by its antenna feed structure 14. This blockage causes discontinuities in the illumination of the parabolic collector surface 12, which are manifested by an increase in undesirable sidelobe levels. FIG. 2 shows an antenna pattern of a parabolic antenna, such as the antenna 10 shown in FIG. 1, in which the sidelobe levels 16 have been increased due to blockage by its feed structure 14.
Therefore, there is an obvious need for a method of reducing the effects of collector surface blockage by feed structures and/or subreflectors in all types of reflector antennas.